: I'm laying out a new master bath on the 2nd floor of our 90 year old house. We will be adding a new stack which will tie into the existing in the basement, but the new stack will be in the corner of the new bath. This leads to the problem. I would like to locate the toilet as close as possible to the corner with the stack so I don't have to run 3" drains through the 2x8 joists. Problem is the toilet drain will have to join to a horizontal drain and wet vent (serving the tub and shower). Is it acceptable for the toilet to join the main stack in a horizontal wye with a wet vent serving the tub, shower, and lavatory? See the attached link for a picture of the layout. Any help would be greatly appreciated.